The long term goal of this project is to identify and characterize the molecular mechanisms of glucose transport in mammalian tissue. The goal of this proposal is to investigate structure/function relationships of monosaccharide transport in the human erythrocyte. The specific aims for this application are: (1) to refine and extend a new methodology for irreversibly labeling the glucose transporter in erythrocytes by photoincorporation of cytochalasin B, a potent inhibitor of this system. This technique will be used to probe the structure of the glucose transport system in situ. (2) In conjunction with this technique, membrane crosslinking agents will be used to explore the oligomeric structure and environment of the transporter, as well as functional changes in transport activity due to crosslinking. (3) Methods will be employed using enzymatic degradation of membrane proteins in order to identify the transmembrane arrangement of this protein. This will include attempts to identify the smallest functional fragments of the transporter. (4) Attempts will be made to identify the role of specific membrane lipids or proteolipids in the transport process. (5) Synthesis of additional photoreactive probes of the transporter will also be attempted. These studies may additionally provide a basis for analyzing mechanisms of glucose transport in other systems such as insulin-sensitive tissue, in both normal and disease states.